A sage, married with Lopamudra, the perfect woman. In the sky he is the star Canopus.
He destroyed the demons Ilvala and Vatapati, broke the pride of the Vindhya mountain and when Shiva and Parvati got married and all the gods gathered in the Himalayas, he went south to maintain the balance of the earth.
During a fight of Indra against demons they hid in the ocean. Agastya drank it empty, the Gods could destroy the demons, then he filled the hole again with his urine.
As the father of Tamil language he taught Tamil grammer at Pothigai mountain.